Aircraft wings may comprise devices at their wingtips to change aerodynamic properties of the wings. For example, wing tip fences can act to control vortices at wingtips. Another example is winglets, which typically take the form of small wing-like structures at the end of aircraft wings, and which are angled with respect to the rest of the wing. A winglet may be an upper portion of a wingtip device that is typically angled toward the upper (i.e. suction) surface of the wing, or a lower portion of a wingtip device that is typically angled toward the lower (pressure) surface of the wing. A winglet, for example an upper portion of a wingtip device, can improve the efficiency of an aircraft by improving the lift to drag ratio of a wing. Winglets can also increase effective wingspan without substantially increasing the width of an aircraft. For example, when a wing bends during flight, a lower portion of a wingtip device at the end of the wing can become level so as to provide effective lift, and hence act as a quasi-span extension device. Since the width of an aircraft is often restricted, for example for compatibility with airports, winglets that extend the effective wingspan without extending the width of the plane can be of great utility.
A drawback of some known fittings of winglets to wing portions, such as butt strap fittings, is that interchange of parts so connected can take considerable time and effort, for example, due to the considerable number of components that need to be removed and refitted. Interchange can be particularly burdensome when complex wing geometries are involved, because such geometries can make achieving the required tolerances more difficult.
It would be advantageous for winglets to be easily and quickly attached to, and detached from, wing portions. This would, for example, assist rapid exchange of a winglet for another winglet in the case of damage being sustained by the winglet in use. It would also be advantageous if winglets met interchangeability requirements, i.e. to be able to be taken “off the shelf” and be quickly and easily installed onto and/or removed from a wing portion with minimum reworking of the winglet and/or wing portion.